... the application has been properly compiled, but when I insert a breakpoint and I start debugging after a second show the dialog message with 'The gdb process crashed'.
how can I do to debug the program?

System : Window7
gdb version : Qt SDK version 1.1.3 - Qt libraries version 4.7.4 (GDB Version 6.7.50.20071127) - the full Qt installation download from this site.
... the source show is only part of the .pro file, the project contains the Scintilla source/include files v2.29, my personal Scintilla qt platform implementation sources, and QMainWindow to test the implementation. Problem is that I MUST enter in debug mode to correct the application crashes.

The debugger log is displayed in the debugger view by default. It should be in the top left somewhere (sorry, I have changed the layout quite a bit here and am not sure where that was originally anymore).